Electrophotographic devices, such as printers, copiers or faxes, may use a developing agent, such as toner, to form images on sheets of media. The developing agent may be stored in a cartridge or other device. The developing agent device may be either fixed or removable from said electrophotographic device.
Developing agent devices may incorporate agitators within the cartridges to stir the toner particles during operation, which may help prevent clumps and keep the toner particles fluid. Agitators may include paddles or other members that may sweep the inner surface of the developing sump, or the area of the device in which the developing agent may be stored. As media is fed through the printing device, the agitators may also help feed the developing agent to the developing portion of the printing device.
Developing agent devices may also include sensors, such as optical sensors, to determine when the device is out of developing agent. Optical systems may use transparent windows located within the sump area of the cartridge. A signal emitter and sensor, for example, may be placed in communication with a reflector inside of the sump area. In some instances, signal quality may be correlated with the amount of toner in the sump.